osmocom-sdr February 2017

osmocom-sdr@lists.osmocom.org

14 participants
11 discussions

gr-fosphor CL_INVALID_VALUE in clEnqueueFillBuffer call
by Raj Bhattacharjea 20 Jun '17

20 Jun '17

I'm using the latest fosphor from git (7b6b9961bc2d9b84daeb42a5c8f8aeba293d207c) and am seeing two weird (and I believe related) issues. Firstly, I see the following error: [+] Selected device: TITAN X (Pascal) [!] CL Error (-30, /home/user/gr-fosphor/lib/fosphor/cl.c:409): Unable to queue clear of spectrum buffer This is CL_INVALID_VALUE returning from clEnqueueFillBuffer, so I added some debug fprints to cl.c to see what parameters were being passed into clEnqueueFillBuffer: Edits: fprintf(stderr, "size = %d\n", 2 * 2 * sizeof(cl_float) * FOSPHOR_FFT_LEN); fprintf(stderr, "pattern_size = %d\n", sizeof(float)); fprintf(stderr, "pattern = %p\n", &noise_floor); fprintf(stderr, "offset = %d\n", 0); Output: size = 16384 pattern_size = 4 pattern = 0x7fb66b7fdd2c offset = 0 These parameters look like they shouldn't cause CL_INVALID_VALUE: https://www.khronos.org/registry/OpenCL/sdk/2.0/docs/man/xhtml/clEnqueueFil… But there is this one condition that might be met, which is that somehow size (16384) is larger than the underlying buffer (cl->mem_spectrum). The underlying OpenGL buffer being too small brings me to my next (I believe related) issue. The spectrum plot in fosphor is weirdly pixelated, please see the attachment, which shows a screencap from "osmocom_fft -F -f 100e6 -g 20 -s 10e6". Where is the cl->mem_spectrum buffer ultimately declared / initialized? My OpenCL / OpenGL sharing knowledge is nonexistent, any pointers for how I can help debug this issue? Output of clinfo is attached as well, and I'm on Ubuntu 16.04 on x86_64. -- Raj Bhattacharjea, PhD Georgia Tech Research Institute Information and Communications Laboratory http://www.prism.gatech.edu/~rb288/ 404.407.6622

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RTL-SDR and RTL-TCP drivers
by Krzysztof Halasa 12 Jun '17

12 Jun '17

Hello, it's my first mail on this list, so please forgive me if I do something wrong. I'm about to post a couple of patches for RTL drivers: 1. RTL-SDR: convert _lut to float[] to reduce size by a factor of 256. The _lut is being indexed by I + Q (16 bits = 65536 entries), however both samples can be processed independently, resulting in 8-bit LUT. Saves a bit of RAM and CPU cache. lib/rtl/rtl_source_c.cc | 19 ++++++------------- lib/rtl/rtl_source_c.h | 4 ++-- 2 files changed, 8 insertions(+), 15 deletions(-) 2. RTL-TCP: Convert to single class model The existing RTL TCP driver is quite different from its brother RTL_SDR. It's much more complicated, uses gr::blocks::deinterleave and gr::blocks::float_to_complex, and generally doesn't work correctly (e.g. https://github.com/csete/gqrx/issues/99 Spectrum is mirrored when filter or demodulator changes (rtl_tcp) #99) I've converted the RTL TCP driver to the model used by RTL_SDR, simplifying it in the process, and fixing the GQRX issue. lib/rtl_tcp/CMakeLists.txt | 1 - lib/rtl_tcp/rtl_tcp_source_c.cc | 352 ++++++++++++++++++++++++++++++++-------- lib/rtl_tcp/rtl_tcp_source_c.h | 32 +++- lib/rtl_tcp/rtl_tcp_source_f.cc | 327 ------------------------------------- lib/rtl_tcp/rtl_tcp_source_f.h | 125 -------------- 5 files changed, 309 insertions(+), 528 deletions(-) I'm also thinking about merging the code common to RTL-SDR and RTL-TCP, but this it's done yet. Comments? -- Krzysztof Halasa

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RTLSDR IQ imbalance ???
by a c 27 Feb '17

27 Feb '17

Hello, I use RTL-FM on a raspberry pi3. I notice practically always the presence of a weak carrier accompanying the emission received in AM mode and interferences in NFM mode. When i use rtl-tcp and sdr# or sdrconsole the demodulation is perfect. I assume that IQ amplitude phase correction is involved. I saw in the source of rtlsdr: IQ estimation / compensation (en_iq_comp, en_iq_est) * / Rtlsdr_demod_write_reg (dev, 1, 0xb1, 0x1b, 1); I suppose we use an internal chipset function? Is this function good enough? I did not find anything about it in RTL-FM but I'm not a specialist. Is an improvement possible? Regards, Arnaud

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Floating point error in tuner_r82xx.c
by Steve Knoeck 27 Feb '17

27 Feb '17

Hi, I get a floating point exception when I run rtl_tcp. I traced the error with GDB to line 515 of tuner_r82xx.c if (vco_fra > (2 * pll_ref_khz / n_sdm)) I found that n_sdm was 0. I don't understand how this code work and I'm very new to this software but it sure looks like a programming bug. | 513 /* sdm calculator */|| || 514 while (vco_fra > 1) {|| || 515 if (vco_fra > (2 * pll_ref_khz / n_sdm)) {|| || 516 sdm = sdm + 32768 / (n_sdm / 2);|| || 517 vco_fra = vco_fra - 2 * pll_ref_khz / n_sdm;|| || 518 if (n_sdm >= 0x8000)|| || 519 break;|| || 520 }|| || 521 n_sdm <<= 1;|| || 522 }| If the condition on line 515 ever evaluates to false then vco_fra doesn't get updated. The loop will keep repeating with the same value of vco_fra until n_sdm becomes 0. Steve

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Fwd: How to get out the maximum from cheap sdrs
by Stefan Groißmeier 27 Feb '17

27 Feb '17

Hi All, I would like to realize an algorithm to build the best possible dvb-t sdr experience. The idea is, that no matter how many sdrs and what kind of antenna you have, the software gets the best out of your hardware. This is what I have thought: The user community of a system depends on how useful it is, how easy it is to use, build and how much money it costs. Rtl-sdrs are quite cheap, but for now a user has no benefit of having multiple sdrs in its system. That is why I'm searching a way to correlate the signals of the sdrs without hardware modification. I think everyone of you has seen the noise from the power source. Has anyone tried to build a filter to use that noise to calculate the delay between multiple dongles? I mean, they get the same noise. I don't know if it is sufficient, but it is also a good spot, to put some artificial noise in, as it can be easily accessed and does not interfere with rf circuitry when it is switched off. Is that an useful approach? Do you think this could work? Did I miss something? regards, Steve

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Request
by zainab jeragh 26 Feb '17

26 Feb '17

Hello We are doing a ADS-B reciever senior project, Can we have the building blocks in the gnu radio for that? Please help us We are using the hackrf one hardware Which is the osmocom source in the gnu radio Thanks Sent from my iPhone

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Error "No E4000 tuner found" on rtl_test -t
by Martin McGlensey 26 Feb '17

26 Feb '17

Hello, I recently purchased a NooElec nesdr mini dongle. I want to install it on Linux Mint 17.1. I have rtl-sdr installed. I have blacklisted the dvb_usb_rtl28xxu driver. When I run rtl_test it reports that the dongle is present and sending. When I run rtl_sdr -t to check the tuning range it reports no E4000 tuner found. Called NooElec for tech support. Got link for linux install but got error "page not found". Tried to get on their mailing list from their IE page. Bad gateway error 502. Looks like support may be difficult to get through NooElec. Does this error indicate a defective rtl dongle? Where can I find the install procedure for the NooElec R820T NESDR mini. All responses are appreciated. Thank you, Marty, N3MOW N3mow(a)arrl.net <mailto:N3mow@arrl.net> mmcg29440(a)frontier.net <mailto:mmcg29440@frontier.net>

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Added Bias T set / get to API
by Lucas Teske 20 Feb '17

20 Feb '17

So since there are now three radios (that I know) that has a hardware Bias T support (HackRF, RTLSDR, Airspy) I added a set_biast and get_biast methods to the default Source API. I also added Airspy and HackRF bindings to enable / disable Bias T. The RTLSDR isn't merged into mainstream, so I didn't added anything. There is also the default implementations (doing nothing for set, and returning false for get), so no breaks on the current source or current applications. -- Lucas Teske Teske Virtual System GPG: 4A90 974B ACE0 A9A6 AF09 B3B1 6C39 C1C1 6A9D A7BE

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RTLSDR_Set_tuner_Bandwith error
by Martin McGlensey 13 Feb '17

13 Feb '17

I have a Panadapter program, written in python, that throws an error "undefined symbol Set_Tuner_Bandwith in librtlsdr0" Searching the net I've found that set_tuner_Baandwith may have been dropped from the library. I'm using version 5.3. One web site said that it had been added back in the latest revision v0.7.0. Tried loading the new library and now find that RTL-SDR requires dependencies found in librtlsdr0 version 5.3. Is there a work around to eliminate this error. I did download the latest rtl-sdr but it will not compile because of the dependency problem I did not write the program so I hesitate to take it apart and I have not received much help from the author. BITW I'm not the greatest linux person so I need clear answers. Having said that all responses will be appreciated. 73 Marty, N3MOW

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rtl_fm Squelch Questions
by Martin McCormick 11 Feb '17

11 Feb '17

I have been playing with the rtl_fm program and most of it works amazingly well but I can not seem to get the squelch to stay open when receiving signals. I have not tried to analyze the source yet so I am asking what principle drives this squelch? In the analog world, the best squelches for FM receivers tend to be noise-driven and use a high-pass filter to filter out normal audio. When the noise drops below a preset threshold, the squelch opens. For AM receivers, a cheap and easy solution is to monitor the AGC and open the squelch when there is AGC voltage above a preset level. What I am noticing is that if I set the l value to a point just above where the noise stops, signals do open the squelch but even strong signals will not keep it from flickering on and off constantly. If I set the l value any lower, the squelch is always open so that is not the issue. I have tried signals that are absolutely full-quieting, with and without CTCSS and the squelch opens briefly, closes for a fraction of a second, opens for another fraction of a second and randomly flickers on and off for the whole transmission. On rare occasions, the squelch opens when the signal starts, stays open and then closes properly after the carrier leaves. Some of these signals are even ever so slightly noisy and I have heard this situation with and without PL tones or CTCSS so that doesn't seem to matter. Finally, I thought it might have something to do with too narrow a bandwidth so I increased the sampling rate to 24 K which made no difference at all. If the signal has voice on it, the flickering doesn't seem to be effected by the words. Basically, what is this squelch responding to to keep flapping? Martin McCormick WB5AGZ

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osmocom-sdr February 2017